In accordance with the recent development of nanotechnology, a demand is growing for an extremely micro particle (hereinafter called as a single nanoparticle) of a single nanometer (1˜10 nm). In case of manufacturing the single nanoparticle with high accuracy, since a grinding method has limitations, a method for producing a single nanoparticle by growing a crystal has been developing recently. In this case, it is necessary to measure a diameter of a particle during a process of growing the crystal in real time in order to control, for example, a particle diameter.
As a method for measuring a diameter of a particle among analyzing particles known are various methods such as a laser diffraction method and a centrifugal sedimentation method, however, practically from a view point of a performance and a cost, a photon correlation method that is based on a dynamic scattering theory is one of the most effective methods in order to measure a diameter of a single nanoparticle.
A particle diameter distribution measurement device as being a particle analytical device by the use of the photon correlation method based on the dynamic scattering theory irradiates the laser light on particles that are making the Brownian motion in a sample solution, receives the scattered light due to the particle by the use of a photoelectron multiplier, makes auto-correlation data based on a pulse obtained by shaping a waveform of an electric current signal output by the photoelectron multiplier and calculates particle diameter distribution of a particle group based on the auto-correlation data.
For example, in accordance with the device described in the patent document 1, in order to improve the accuracy of calculating the particle diameter distribution, the detected signal from the detector of the scattered light is processed to be an intermediate function, and the particle diameter distribution is calculated by conducting an inverse operation on the intermediate function, the data used for the inverse operation is extracted at appropriate intervals from all of the data area and a data table is made, furthermore an absolute value of first-order differentiation of the intermediate function is calculated. Then the bigger the absolute value is, the shorter interval the data is extracted at.
In accordance with the device described in the patent document 1, even though a big diameter particle exists, there might be a case that the data relating to the big diameter particle is extracted. In case that the data of the particle whose particle diameter is big is included, there might be a case that the accuracy of calculating the particle diameter distribution is degraded because of depending on the data of the particle whose diameter is big.
For the particle diameter distribution measurement device wherein the correlator or the counter is of a linear sampling method, the pulse number obtained by processing the electric current signal output from the photoelectron multiplier as being a detector of the scattered light is counted based on the pulse number received by the multiple multibit counters each of which has the gate and that are arranged in parallel in a state that the gate is open. Ordinarily, the time period while the gate of the multibit counter is open (hereinafter called as the gate time) is set by trial and error by a user of the particle diameter distribution measurement device prior to an actual measurement of the sample. Namely, the user repeats the measurement of the particle diameter distribution while changing the gate time, reviews the auto-correlation function obtained by the result of the measurement for every changed gate time and sets the optimum gate time based on the result. As a result of this, it might happen that is not necessarily the optimum setting. In addition, it takes time and labor prior to setting the gate time.